G.f. satisfies A(x) = 1 + x * A(x * (1 + x^3)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =4a(7) =7a(8) =11a(9) =22a(10) =49a(11) =104a(12) =212a(13) =471a(14) =1112a(15) =2584a(16) =6000a(17) =14574a(18) =36488a(19) =91148a(20) =230011a(21) =596893a(22) =1574433a(23) =4171388a(24) =11193376a(25) =30594229a(26) =84527225a(27) =235243027a(28) =662702701a(29) =1891111335